Insulated electrical conductor



- Patented Nova", 1936 PATENT OFFICE 2,060,858 INSULATED ELECTRICALCONDUCTOR John M. De Bell, Newark, Del.,

aasignor to Hercules Powder Company, Wilmington, Del., a corporation ofDelaware Y No Drawing. Application April 20, 1935, Serial No. 17,471

8 Claims.

This invention relates to an insulated electrical conductor.

The insulated electrical conductor in accordance with this inventioncomprises an electrical conductor in combination with an insulatingmaterial composed of a resinous composition known as extracted pine woodpitch, which is a residue comprising oxidized resin acids such asabietic acid, oxidized terpenes, poiyphenols, polymerized 10. terpenesand frequently some ligneous matter left after the separation of rosin,turpentine and other more valuable constituents of pine wood.

The insulated electrical conductor in accordance with this inventionwill be found to be highly efiicient due to its high dielectricstrength,

especially under impulse tests, and the insolubility of the extractedpine wood pitch, in oils, as transformer oils.

The pine wood pitch for the production of the insulated conductor inaccordance with this invention, as has been indicated, is obtained inconnection with the production of wood rosin from pine wood. The pinewood pitch will comprise oxidized resin, oxidized abietic acid, oxidizedterpenes, polyphenols, polymerized terpenes, and more or less ligneousmatter, but will diiier somewhat in its specific characteristics, suchas acid number, melting point, petroleum ether solubility and content ofnaphtha and toluol soluble matter, depending upon the method for therecovery of rosin from pine wood used in its production.

As is well known, rosin is extracted from pine wood by the'use of asuitable solvent, such as hot gasoline, or benzol, after steaming of thewood with live steam to remove volatile oils, such as turpentine and'pine oil. Again, volatile oils, as turpentine, and pine oil, areextracted with the rosin without first steaming for their removal. 40Following extraction the extract is distilled for the removal of solventwhere the wood was subjected to steaming before extraction and for theremoval of solvent and volatile oils, as t pentine and pine oil, wherethe wood. was en treated directly without ste s. As the result ofdistillation a resinous nu erial consisting of a mixture oi rosin,oxidized abietic acid, oxidised terpenes, polyphenois, polymerizedterpenes and ligneous matter is obtained. This resinous me.- terial maybe treated in any one of a number of ways, all known to the art, for theremoval or refined rosin. The residue remaining after the removal orrefined rosin and including oxidized abietic acid, oxidized terpenes,poiyphenols, poly- 6b merized terpenes and limeous matter originallypresent in the extract and comprising a dark colored, hard, resinousmass constitutes the pine wood pitch.

The exact properties or the pine wood pitch obtained as indicated abovewill depend upon the method used for original extraction from the wood.When the wood is steamed before solvent extraction, a pine wood pitch isobtained having somewhat different properties from that obtained whenthe wood is extracted without steaming. 10 Likewise the properties ofpine wood pitch are somewhat difierent when obtained by differentmethods of purification of rosin. A comparison of the properties ofthree pine wood pitches is given in the following table, in which PitchA is 15 that obtained by extraction of 'wood with hot petroleum solventssubsequent to the removal of the volatile oils by steam distillation,refining with furiural, evaporation of furfurai to leave a resinous massand then extraction of this mass with a petroleum solvent to removepetroleum soluble resin. Pitch B is that obtained by a benzol extractionof unsteamed wood, evaporation of the benzol solution of the residue inhot low boiling petroleum solvent, precipitation of the Pitch B 25 bywashing with cold water, and then removal of this precipitate byfiltration. Pitch C is obtained by the evaporation of the furiurallayer, after refining oi the gasoline solution ofthe crude resinobtained by the benzol extraction of pine wood. 30

Pitch Pitch Pitch A B o Melting point (Hercules drop method)... 91' 0.115 0. 102 C. 35 Acid number 105 116 Unsaponiflable matter 5% 8% V. M. &P. naphtha insoluble 89.5% 96% 83% Toluol soluble 40% 98% Petroleumether insoluble 92. 0% 99% 95% Saponification number. 169 Ash .0ac%.022%

It wiil be noted that while this extracted pine wood pitch containsoxidized rosin or abietic acid, certain of its properties are entirelydifiz'erent from those of so-called oxidized rosin 45 produced byoxidation of rosin. Thus, for example, extracted pine wood pitch issubstantialiy insoluble in natural petroleum hydrocarbons while oxidizedrosin is readily soluble in these solvents. 50

The insulated electrical conductor in accordance with this invention mayinclude the ex tracted pine wood pitch alone or in admixture with othersubstances which may desirably be admixed with it .tor variation oi itsphysical 55 characteristics, such, for example as wood pitch, copal,coal tar asphalt, small amounts of castor oil, rubber, a rosin residueresulting from the steam distillation of pine oil, etc.

The insulated electrical conductor in accordance with this invention maybe of any type or form, however, for convenience I will proceed with amore detailed description of this invention with reference to itsapplication to transformer coils in connection with which it isespecially advantageous, more particularly in view of its very highresistance to impulse te ts and its insolubility in transformer coils.

In the production of a transformer coil embodying this invention, thecoil is wound as usual,

using any desired insulated wire for the winding and the coil beingofany desired form or capacity. After the coil is completely assembled, itis electrically insulated and mechanically bonded in any suitable orwell known manner with the extracted pine wood pitch, described above,either alone or in combination with other desired ingredients. such ashave been indicated by way of example.

By way of example the coil may be insulated and bonded in a well knownmanner by placing it in a tank, placing the tank under vacuum, runningthe extracted pine wood pitch in at a temperature at which it will befluid and then draining off excess pine wood pitch after the desiredimpregnation has been efiected. on cooling, the coil will be found to beeiliciently insulated and bonded.

The impregnation may be eiiiciently accompiished with the extracted pinewood pitch alone or in admixture with other ingredients, at atemperature of about C. to about C.

Where it is not desired to use extracted pine wood pitch alone, mixturesmade up on any of In the production of insulated conductors inaccordance with this invention, it will be desirable, though notessential, that the pine wood pitch be subjected to heat treatment priorto use alone or in admixture, in order to avoid foaming during theimpregnation of a conductor under elevated temperature at which it willbe fluid. By way of illustration, the extracted pine wood pitch'rnaydesirably be treated at a temperature of from about 150 C. to about 325C. for a period of from about 10 minutes to about 2 hours, dependingupon the temperature. More specifically, the pine wood pitch, it treatedat a temperature of about 250 C. for about one i. In combination anelectrical conductor and an insulating material therefor comprising apine wood pitch obtained by the extraction of pine wood and comprisingoxidized resin acids, oxidized terpenes, polyphenols and polymerizedterpenes.

2. A transformer coil including windings of insulated conductivematerial impregnated and bound with a pine wood pitch obtained by theextraction of pine wood and comprising oxidind resin acids, oxidizedterpenes, polyphenols and polymerized terpenes.

3. In combination, an electrical conductor and an insulating materialtherefor which is impregnated with a pine wood pitch obtained by theextraction of pine wood and comprising oxi dized resin acids, oxidizedterpenes, polyphenols, and polymerized terpenes.

4. In combination, an electrical conductor and an insulating materialtherefor comprising aaphalt and a pine wood pitch obtained by theextraction of pine wood and comprising oxidlned resin acids, oxidizedterpenes, polyphenols, and polymerized terpenes.

5. In combination, an electrical conductor and an insulating materialtherefor comprising castor oil and a pine wood pitch obtained by theextraction of pine wood and comprising oxidised resin acids, oxidizedterpenes, polyphenols, and polymerized terpenes.

6. In combination, an electrical conductor and an insulating materialtherefor which is impregnated with a composition comprising 10 parts byweight of asphalt and 90 parts by weight of a pine wood pitch obtainedby the extraction of pine'wood and comprising oxidized resin acids,

oxidized terpenes, polyphenols, and poiymeriaed terpenes.

7. In combination, an electrical conductor and an insulating materialtherefor which is impregnated with a composition comprising 10 parts byweight of castor oil and 90 parts by weight of a pine wood pitchobtained by the extraction of pine wood and comprising oxidized resinacids, oxidized terpenes, polyphenols, and polymeriled terpenes.

8. In combination, an electrical conductor and an insulating materialtherefor comprising a pine wood pitch obtained by the extraction of pinewood and heat-treating to prevent foaming thereof, and comprisingoxidized resin acids, oxidized terpenes, polyphenols, and polymerizedterpenes;

JOHN M. DE BELL.

